For systems that include compressors, pistons must be properly lubricated during operation to reduce wear and avoid damage. For example, oil stored in a crank case is generally used for the lubrication function. If the oil level falls to a level that is too low to provide proper lubrication, damage may result from operation.
Liquid level monitors are known. An oil level monitor can be used to sense a low oil level and send a signal to identify the condition or disable or otherwise shut down the system if too low a level is reached. The operable signal from the oil level monitor can be communicably coupled (e.g. wired) to flash a warning light, sound a howler, shut off electrical power to the system, or send signal a detection signal to a supervisory computer. Such oil level monitors generally need to be compact, low cost and reliable.
For example, one known oil monitor comprises a magnetic reed switch. The liquid to be monitored, such as oil, is piped directly into the monitor through a small metal tube into the float chamber. A float carries a ring magnet inside the chamber and moves up and down on a central pipe which encloses a magnetic reed switch. When the oil level recedes, the float is lowered and the magnet actuates the reed switch at a predetermined level. Although the magnetic reed switch is not susceptible to oil contamination, reed switches typically can not handle the high electrical current and voltage requirements of conventional industrial applications that oil monitors are generally used in.